Manufacture of hydrogen cyanide



Patented Dec. 14, 1948 2;s55,9s"z

Leonard Fallows and Eric VermmMellers; Spon H 1 din'i neainDerby;llmglandsv assignorgiby meshes assigmnents torfieianese (Jorporation rifAjr'nerica a corporationaotDelaware N'o DraWin'g; Kpplication October 3, 1945, Seriali. I, No? 62-0,1\9'I". In Great BritaimOetobenZS, 1944s eoisimsi. 01. 23 -451 This: inventi'ont. relates to; the manufactures of. hydrogen. cyanide; by reactiom betweenacarbon monoxide and ammonia: inc the presence of. a

selecting. the:- reaction conditionss; to. reduce: the:-

extentzto whi'chithe' first itwoz reactions occuraso that they become ofisecondaryximportance only; thezreaotiom. ofiitheicanbommonox-ide with water vapour: isrmuc'himoiier diflicult. 13011 suppress. This:

is thefmoret-nn-fontunatei in thatitlie presence of carbon .di'oxideiin; the reaction": zone: rapidly/res. ducess therefii-ciency of many ofrrth'e: most: active-:1

catalysts: forrtheis main; reaction;

moonsideiiabieinumber oisubstancesrhave boom proposed as'natalys'ts, butialhofzthemr suffer. one? or: more=+ disadvantages. of: them:v are-a rather expensive, andi-m'anya'acfi aszoaztalystseton the: sidesreactionstmentfonechabovaas well: as for the: mainzreactiona reducing: the proporrti'on':.-

oi? the: ammonia Which. is: convertedii intolhydiioa gem cyanide: Moreover; th'osezt. entire: knowm.

to -providez err-catalyst for theiproductionzofinhydro gen oyanidafiromiammoniaiandvcarbonmonoxide:

which is easily andiiche'etply obtainemtis='robust,.,;

gives rise: tot little orrnorcarbons. dioxide;\, maintainsi its: activitio for considerable: periods under. the reaction- :conditions,..;and is capable of con verting; a satisfactorily high proportion: of: thee ammonia'iinto hydrogenzcyanides cyanideisz made-by? bringing a" gasimixtu-rezoomprising carbon monoxide' andzammonia intoiconstact with: manganese dioxide as catalyst await Thamanganeseidioxideimayxbeiinrpowdeniormz 1 temperature? above145062;:v 1

According to the present invention hydrogen.

or depositedon a carrier, but it' is. preferably used in ltfie. formof a. composition made; by setting a mixtureofl' manganese dioxide and" cement with atalyst; wat'erL Alvery 'usefifl' catalyst. composition may Itiis'. knowmtiiati monoxide: andi amw 5 beima'de'by mixingimanganesedioxide with to mania: be: causew to: react as ate produce; 6} times; its weight. of? Portland cement, forming. hydmgemcyanideebyrheatingzthem... n2:the'xpr.es;--v themix'tureii'nto. a sliirry with water andallowenoeeofl suitable-catalysts: flnfortunatelmshoww ingotfie sl'urpyto set in the form of'thin slabs. ev'enithemalueoot:this:method:oimakingr;hydro--- The composition is preferablyallowed to. age forgemcyaniderissconsidemlriiy'redncedi.by:the-fact: 10 aboutl3. to 6"months aften which it is ready. for that; certaini undesired side reactionssitendi to use. p y 00cm: smmltan'enuslyi with; the. tormationoi.hye Manganese dioxide catalysts and especially drogen cyanide. The mosttimportant (ma-theses manganese dioxide-cementcompositions, havea side) reactions fiIBEth'EadGOOII-IPOSitiOIT offth'e aliinumber of' advantages over other substances, moiii-a: toxniirogen1and;hydrogernthe:decomposie which have been proposed as catalysts for the tiom oizthezcarbon monoxide toicarbonxandmari production of hydrogem cyanide from carbon b'ona. dioxide; and; the reaction between: carbonr monoxideandrammoniav Notonlyarethey active 7 monoxideiandswaterr'vap'ouni(whicH-isMormedx incausing the formation of. hydrogencyanide inethrnmain reaction) td giyei hydrogenrandicar with littleorrnoicarbon dioxide,- .but.they maintain. b'undioxid'ea r iltliougl izitimpossible by carefullwtheir. activity fonlongperiods under. the reactionconditionsa Furthermore, manganese. dioxidecementtoompositionsare-cheap, robustguandeasily made andbhandled The reaction between' ammonia may for. example. be carried outby passing-the gasesithroughan iron or other suit.- able tube containing the catalyst. The tube may be-heatedlto any temperature between about 450 and '700P.C., butweprefer to employ temperatures.

between: about-500. and 650 C.,..especial1y be-- tweenrabout550? and-650 Ct Generally speak ing. thezhigher. the. temperature. within the range 4509-7009 .Gsthehighenis the proportion of ammoniawhiohistoonvertedvinto hydrogen cyanide,

. butgattthe.samegtimethe proportionl'ostby side] reactions-is alsoihigher Moreover while. atrtempera-tures-oi,about. 500 -550' C1 the amount. of

car-bonrd-ioxide forined isoften. so. small that it? cannotebe. determined by the ordinary methods.

of. gasv analysis-,, at higher temperatures. the amountiiormedi increases. although within the temperature range. specified} it never becomes serious.

The pressure of the gas'es iri the reaction zone may be. atmospheric;=. although. if desired higher pressures: may; be usedl. The carbon monoxide and. ammoniarmay if desired be 7 used in. admixture: with'icertaing other gases, for example nitroarexusedin fthe'gabsenceof substantial amounts. of othengases.

Aithouglrequai 'inolecular proportions .of car .the carbon monoxide-and.

bon monoxide and ammonia take part in the reaction, the proportion of the ammonia converted into hydrogen cyanide is, if the other conditions are kept constant, higher if the ammonia is mixed with a considerable excess of carbon monoxide. For example, for every molecular proportion of ammonia in the initial gas mixture, there may with advantage be more than 3, for example from 6 to 40, molecular proportions of carbon monoxide. Unreacted carbon monoxide can be recycled. The space velocity of the gas mixture through the reaction zone may vary over a wide range, for example between about 10 and 100 litres of ammonia (at normal temperature and pressure, i. e., at 0 C. and 760 mm. of mercury) per hour per litre of catalyst. I

The gases leaving the reaction zone contain, besides hydrogen cyanide, unchanged carbon monoxide and also as a rule some unchanged ammonia, together with water vapour, some hydrogen and nitrogen, and sometimes a very small amount of carbon dioxide. In order to isolate the hydrogen cyanide from this mixture, it'is preferable first to wash the gases with an anhydrous relatively weak acid, for example glacial acetic acid, so as to remove ammonia, and then to condense the hydrogen cyanide and water vapour by intensive cooling. The condensate may contain, beside aqueous hydrogen cyanide, a certain amount of the washing acid and its ammonium salt, but the hydrogen cyanide is easily isolated by fractional distillation.

The invention is illustrated by the following examples.

Example I Manganese dioxide was intimately mixed with three times its weight of cement, and sufficient water was then added to form a slurry. The slurry was spread into thin sheets and allowed to set, after which the sheets were kept for six months and then broken up and screened.

A gas mixture consisting of volumes of carbon monoxide and 1 volume of ammonia was passed through'an iron tube containing a manganese dioxide catalyst prepared as above described; the tube was heated to 610 C'., and the space velocity of the gas was 11 litres of ammonia per hour per litre of catalyst, i. e. about 230 litres of the gas mixture per hour per litre of catalyst. On leaving the tube the gaseous products were met by a stream of glacial acetic acid in amount at least sufiicient to combine with all the unchanged ammonia, and were then cooled sufficiently to condense the hydrogen cyanide formed in the reaction. The condensate was subjected to fractional distillation whereby the hydrogen cyanide was isolated in a substantially pure state. The amount of hydrogen cyanide obtained corresponded to about 43% of the ammonia used, and a further 18% of the ammonia was recovered as ammonium acetate.

Example II Example III The procedure described in Example I was used with a gas mixture consisting of about 8 volumes of carbon monoxide and 1 volume of ammonia. The tube was heated to 630 C. and the space velocity was about 70 litres of ammonia (630 litres of the gas mixture) per hour per litre of catalyst. About 40% of the ammonia was converted into hydrogen cyanide.

Example IV The procedure of Example I was used with a gas mixture consisting of 6 volumes of carbon monoxide to 1 volume of ammonia. The tube was heated to 550 0., and the space velocity was about litres of ammonia (315 litres of the gas mixture) per hour per litre of catalyst. The proportion of the ammonia converted to hydrogen cyanide was about 36%, and over of the ammonia was recovered as ammonium acetate.

Having described our invention, what we desire to secure by Letters Patent is:

1. Process for the manufacture of hydrogen cyanide, which comprises passing ammonia mixed with at least an equal volume of carbon monoxide and substantially free from oxidizing gases in contact with a catalyst which, at the beginning of the reaction, comprises manganese dioxide at a space velocity of at least 10 litres of ammonia, measured at 0 C. and. 760 millimeters of pressure, per hour per litre of catalyst and at a temperature above 450 C.

2. Process for the manufacture of hydrogen cyanide; which comprises passing ammonia mixed with at least 3 times its volume of carbon monoxide and substantially free from oxidizing gases in contact with a catalyst which, at the beginning of the reaction; consists'of manganese dioxide set in cement at a space velocity of at least 10 litres of ammonia, measured at 0: C. and 760 millimeters of pressure, per hour per litre of catalyst and at a temperature above 450 C.

3. Process for the manufacture of hydrogen cyanide, which comprises passing ammonia mixed with 6 to 40 timesits volume of carbon monoxide and substantiallyfree from oxidizing gases in contact with .a catalyst'which, atthe beginning of the reaction, comprises manganese dioxide at a space velocity of 10 to litres of ammonia, measured at 0 C. and 760 millimeters of pressure, per hour per litre of catalyst and at a temperature of 500 to 650 C.

4. Process forthe manufacture of hydrogen cyanide, which comprises passing ammonia mixed with at least 3 times its volume of carbon monoxide'and substantially free from oxidizing gases through a tube containing a catalyst which, at the beginning of the reaction,'consists of manganese dioxideset in'l to 6 timesits weight of cement at a space velocity of 0 to 100 litres of ammonia, measured at 0 C. and 760 millimeters of pressure, per hour per litre of catalyst and at a temperature of 450 to 700 C.

5. Process according to claim 4, wherein the catalyst is made by setting a mixture of manganese dioxide with '1.to 6 times its weight of cement by means of water and allowing the composition so obtained to age for 3 to 6 months before use.

6. Process for the manufacture of hydrogen .cyanide, which comprises passing ammonia mixed with 6 to 40 times its volume of carbon monoxide and substantially free from oxidizing gases througha .tube containing a catalyst which, at

the beginning of the reaction, consists of manganese dioxide set in 1 to 6 times its weight of cement at a space velocity of 1-0 to 100 litres of ammonia, measured at 0 C. and 760 millimeters of pressure, per hour per litre of catalyst and at a temperature of 500 to 650 C.

'7. Process for the manufacture of hydrogen cyanide, which comprises passing ammonia mixed with 6 to 40 times its volume of carbon monoxide and substantially free from oxidizing gases through a tube containing a catalyst which, at the beginning of the reaction, consists of manganese dioxide set in 1 to 6 times its weight of cement at a space velocity of 10 to 100 litres of ammonia, measured at 0 C. and 760 millimeters of pressure, per hour per litre of catalyst and at a temperature of 500 to 650 C. and substantially immediately afterwards freeing the resulting gas mixture from unreactecl ammonia by treatment with acid and-then cooling it sufliciently to condense substantially all the hydrogen cyanide formed.

8. Process according to claim 7, wherein the catalyst is made by setting a mixture of man- 6 ganese dioxide with 1 to 6 times its weight of cement by means of water and allowing the composition so obtained to age for 3 to 6 months before use.

LEONARD FALLOWS. ERIC VERNON MELLERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Frazer Oct. 12, 1926 OTHER REFERENCES Number Reinhold 

